Technical Field
The present invention relates to a rectifier circuit that converts an AC (alternating current) signal to a DC (direct current) signal.
Background Arts
A rectifier circuit that electrically converts an AC signal (AC power) to a DC signal (DC power) is used for a circuit to obtain DC power from a high-frequency weak signal received by an antenna in a passive-type RFID (radio frequency identifier) tag, or to obtain DC power from AC power that is converted from mechanical energy such as weak vibration energy using a mechanical-electric coupling system.
Examples of such a rectifier circuit include a CMOS (complementary metal-oxide-semiconductor) rectifier circuit that performs all-wave rectification on an AC signal by a differential operation to obtain a DC signal, and outputs the DC signal to a load. In a CMOS rectifier circuit, for example, a first half-wave rectifier circuit and a second half-wave rectifier circuit, which have a CMOS configuration by an N-channel type MOS transistor and a P-channel type MOS transistor, are connected in parallel, and are operated in opposite phase to each other by differentially input AC signals, thereby constituting a whole-wave rectifier circuit as a whole. Each MOS transistor functions as a switch, and the gate electrode is connected to an AC signal node of opposite phase to the AC signal applied to the source electrode and the drain electrode.
In this CMOS rectifier circuit, the gate electrode of each MOS transistor is connected to the AC signal node of opposite phase, and therefore, the ON voltage and the ON resistance during the forward operation of the switching circuit can be reduced and the reverse leak current can be reduced. However, if the input AC power is large and the output DC voltage is large, the excessive gate electrode DC bias of each MOS transistor would increase the leak current during reverse operation, which degrades the efficiency of the power conversion.
In order to solve this problem, there is a rectifier circuit described in Japanese Patent Application Laid-open Publication No. 2008-11584, for example. Specifically, in the rectifier circuit, a capacitor is inserted in a connection line between the gate electrode of each MOS transistor and the AC signal node of opposite phase. Accordingly, an AC signal that is superimposed on a DC signal (a signal in which an AC component is superimposed on a direct current) is supplied to the gate electrode of each MOS transistor. Further, in the rectifier circuit, the gate electrode of each MOS transistor and the DC terminal are connected to each other via a resistance element.